There is no word like "Grassation" in the English language. Therefore, there are no antonyms for this word. However, we can suggest some antonyms for the word "grass." Some of the antonyms for the word "grass" include concrete, pavement, asphalt, stone, and dirt. These words represent opposite ideas to grass, which is natural, green, and organic. In some contexts, these antonyms can be seen as negative opposites of grass, such as when referring to urbanization or environmental degradation. However, in other contexts, they can be seen as neutral or positive opposites, such as when referring to alternative landscaping or building materials.